Cooling systems have been changing from air cooling to liquid cooling in view of higher parts packing densities and efforts to save space and energy in data centers. As liquid immersion cooling systems are introduced for liquid cooling, inactive refrigerants are finding use therein. It has been customary to immerse electronic parts entirely in an inactive refrigerant having a high boiling point in an open cooling bath for thereby cooling the electronic parts.
Inactive refrigerants are low in thermal conductivity than water and are highly costly. It has been desirous of reducing the amount of an inactive refrigerant used for liquid immersion cooling. According to an aspect of the present embodiment, it is an object of the present embodiment to reduce the amount of an inactive refrigerant used.
The followings are reference documents.    [Document 1] International Publication Pamphlet No. WO 2012/025981,    [Document 2] Japanese Laid-open Patent Publication No. 4-170097, and    [Document 3] Japanese National Publication of International Patent Application No. 2011-518395.